In recent years, many different additive manufacturing techniques for the fast production of three-dimensional objects have been developed. Additive manufacturing and related variations thereof are sometimes referred to as 3D printing, solid imaging, solid freeform fabrication, rapid prototyping and manufacturing and the like. Additive manufacturing includes many different techniques for forming three-dimensional objects on a layer-by-layer basis from a build material utilizing layer or sliced data representing cross-sections of the objects. These techniques include, for example, extrusion-deposition or selective deposition modeling (SDM) techniques such as fused deposition modeling (FDM) and fused filament fabrication (FFF), stereolithography (SLA), polyjet printing (PJP), multi jet printing (MJP), selective laser sintering (SLS), three-dimensional printing (3DP) techniques such as color-jet printing (CJP), and the like.
A number of additive manufacturing techniques form a three-dimensional object from a corresponding digital model, which is often provided by a computer-aided design system (this digital model at times referred to as a CAD model). The digital model may represent the object and its structural components by a collection of geometry. This digital model may be exported to another form that represents the closed-form surface geometry of the object, which at times may be referred to as a shell. In some examples, the shell of an object may take the form of a mesh of polygons (e.g., triangles), such as in the case of an STL (standard tessellation language) model or file. The shell of the object may then be sliced into layer data that defines layers of the shell. This layer data may be formatted into an appropriate language that describes a tool path for forming the object, which may be received by an additive manufacturing system to manipulate build material to form the object on a layer-by-layer basis.
Additive manufacturing techniques are evolving to incorporate build materials having different properties in the formation of a single object, which may permit more complex objects such as multi-colored objects. A number of techniques have been employed to prepare the data required to guide formation of such an object. One technique involves the initial creation of separate solid models for separate portions of an object to be formed from respective build materials, from which separate shells may be separately created and processed. But this technique requires the expertise of the CAD or other system used to create the solid models, and the added resources required to separately process each of the solid models.
In another technique, a single shell may be broken apart into usable portions. According to this technique, the shell may be separated into fragments, such as along well-defined edge lines. Once separated, the original closed-form shell now includes multiple unclosed-form fragments. The unclosed fragments must then be healed to form corresponding closed-form fragments that they may be separately sliced into respective layer data. This process is often complicated, requiring high-performance processors. The process also has a tendency to create non-symmetrical faces resulting in a poor match when the fragments are rejoined during formation of the object. This drawback may be amplified when dealing with shells that do not have well-defined edge lines such as those created from scanned (e.g., point-cloud) data.
Therefore, it may be desirable to have an apparatus and method that improves upon existing techniques.